ABSTRACT
BACKGROUNDS: In order to provide a long-lasting formulation for spinosad (SP) targeting larval stages of Aedes aegypti (Linnaeus) and others alike, a SP tablet was developed based on microspheres, using polylactic acid as inside coating material. The microspheres were encapsulated using polyethylene glycol and 1-hexadecanol to form a sustained-release SP tablet. Micromorphology, active ingredient loading, structure identification, photolysis resistance and biological activity were evaluated in this report. RESULTS: (i) The SP microspheres had an average particle size of 6.16 ± 2.28 µm, low adhesion and good dispersion as evaluated by scanning electron microscopy and morphology. (ii) The average active ingredient loading and encapsulation of SP microspheres were 32.80 ± 0.74% and 78.41 ± 2.22%, respectively. (iii) The chemical structure of encapsulated SP was confirmed by Fourier transform infrared and 1H-nuclear magnetic resonance. (iv) The photostability of the microspheres and the tablets were evaluated. The results showed that DT50 (time required to dissipate 50% of the mass originally present) of SP was 0.95 days in microspheres and 6.94 days in tablets. (v) The long-term insecticidal activity of SP tablets was investigated, and the tablet had a long-lasting activity against the mosquito larvae, showing 100% larval mortality for 63 days. CONCLUSIONS: The study provided a new long-lasting formulation of SP, which displayed good efficacy in the control of Ae. aegypti larvae. © 2024 Society of Chemical Industry.
ABSTRACT
@#Abstract: Objective In order to explore the application prospects of the phenyl pyrazole insecticide fipronil for mosquito control and identify potential target genes involved in the resistance of Aedes aegypti to fipronil, and lay the foundation for an in-depth study of the resistance mechanism of Aedes aegypti to fipronil. Methods Using Aedes aegypti sensitive strains as experimental materials, Aedes aegypti larvae were treated with fipronil, and the differences in gene expression of Aedes aegypti larvae before and after drug administration were compared at the transcriptome level using transcriptome sequencing combined with bioinformatics analysis, and the differential genes were analyzed. Results A total of 757 differentially expressed genes were identified between the fipronil-treated group and control group, including 217 and 540 up- and down-regulated genes, respectively. Among these, the expression of glutamate-gated chloride channel (GluCls) genes varied significantly before and after treatment. Gene ontology analysis revealed that differentially expressed genes were enriched in catalytic activity, binding, metabolic processes, and membrane-related functions, while KEGG pathway analysis indicated enrichment in biosynthesis, metabolism, and life regulation processes, while the glutathione metabolic pathway was enriched in 15 differentially expressed genes. Conclusions The transcriptome results revealed that GST gene expression was significantly upregulated in fipronil-treated Aedes aegypti larvae, indicating that GST gene is involved in the development of fipronil resistance in Aedes aegypti larvae. In addition, GluCls gene expression was also significantly different before and after treatment, suggesting that GluCls migh be a potential target receptor for fipronil resistance in Aedes aegypti. As GluCls is an ideal target receptor found only in invertebrates, this discovery provides a reference and basis for further exploration of the toxicological mechanism of fipronil on Aedes aegypti.
ABSTRACT
Rhipicephalus sanguineus, the brown dog tick, is the most widespread tick in the world and a predominant vector of multiple pathogens affecting wild and domestic animals. There is an increasing interest in understanding the role of tick microbiome in pathogen acquisition and transmission as well as in environment-vector interfaces. Several studies suggested that the tick microbial communities are under the influence of several factors including the tick species, dietary bloodmeal, and physiological stress. Compared with insects, very little of the microbial community is known to contribute to the nutrition of the host. Therefore, it is of significance to elucidate the regulation of the microbial community of Rh. Sanguineus under starvation stress. Starvation stress was induced in wild-type adults (1 month, 2 months, 4 months, 6 months) and the microbial composition and diversity were analyzed before and after blood feeding. After the evaluation, it was found that the microbial community composition of Rh. sanguineus changed significantly with starvation stress. The dominant symbiotic bacteria Coxiella spp. of Rh. sanguineus gradually decreased with the prolongation of starvation stress. We also demonstrated that the starvation tolerance of Rh. sanguineus was as long as 6 months. Next, Coxiella-like endosymbionts were quantitatively analyzed by fluorescence quantitative PCR. We found a pronounced tissue tropism in the Malpighian tubule and female gonad, and less in the midgut and salivary gland organs. Finally, the blood-fed nymphs were injected with ofloxacin within 24 h. The nymphs were allowed to develop into adults. It was found that the adult blood-sucking rate, adult weight after blood meal, fecundity (egg hatching rate), and feeding period of the newly hatched larvae were all affected to varying degrees, indicating that the removal of most symbiotic bacteria had an irreversible effect on it.
ABSTRACT
Culex quinquefasciatus, one of the most significant mosquito vectors in the world, is widespread in most parts of southern China. A variety of diseases including Bancroft's filariasis, West Nile disease, and St. Louis encephalitis could be transmitted by the vector. Mosquitoes have been shown to host diverse bacterial communities that vary depending on environmental factors such as temperature and rainfall. In this work, 16S rDNA sequencing was used to analyze the seasonal variation of midgut bacterial diversity of Cx. Quinquefasciatus in Haikou City, Hainan Province, China. Proteobacteria was the dominant phylum, accounting for 79.7% (autumn), 73% (winter), 80.4% (spring), and 84.5% (summer). The abundance of Bacteroidetes in autumn and winter was higher than in others. Interestingly, Epsilonbacteraeota, which only exists in autumn and winter, was discovered accidentally in the midgut. We speculated that this might participate in the nutritional supply of adult mosquitoes when temperatures drop. Wolbachia is the most abundant in autumn, accounting for 31.6% of bacteria. The content of Pantoea was highest in the summer group, which might be related to the enhancement of the ability of mosquitoes as temperatures increased. Pseudomonas is carried out as the highest level in winter. On the contrary, in spring and summer, the genus in highest abundance is Enterobacter. Acinetobacter enriches in the spring when it turns from cold to hot. By studying the diversity of midgut bacteria of Cx. quinquefasciatus, we can further understand the co-evolution of mosquitoes and their symbiotic microbes. This is necessary to discuss the seasonal variation of microorganisms and ultimately provide a new perspective for the control of Cx. quinquefasciatus to reduce the spread of the diseases which have notably vital practical significance for the effective prevention of Cx. quinquefasciatus.
